Display screen or portion thereof with transitional graphical user interface



FIG. 1 shows a first image of a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 shows a second image thereof;

FIG. 3 shows a third image thereof;

FIG. 4 shows a fourth image thereof; and,

FIG. 5 shows a fifth image thereof.

The peripheral dashed broken lines illustrate a display screen or portion thereof, and form no part of the claimed design.

The remaining dashed broken lines illustrate portions of the transitional graphical user interface which form no part of the claimed design.

The appearance of the graphical user interface transitions between the images shown in FIGS. 1-5. The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 